Lecture 5 Bone Tissue

What are the 4 main components of the Skeletal system?

Bones, Cartilages, Ligaments, and Support Cells

Bones

Hard, rigid organ of mineralized collagen matrix

Cartilages

Tough and flexible connective tissue

Ligaments

Tough, fibrous band of connective tissue that holds bones

What is Bone (osseous tissue)

connective tissue with a matrix hardened by calcium phosphate deposition

Osteology

study of bone

Mineralization (calcification)

hardening of bone matrix

What are other bone components?

blood, bone marrow, cartilage, adipose tissue, nervous tissue, fibrous connective tissue

What are the functions of the skeleton?

Support, Movement, Protection, Blood formation, Electrolyte balance, Acid-base balance, hormone secretion, and Detoxification

What are the different bone shapes?

Flat bones - thin curved plates; cranial

Long bones - long with expanded ends; limbs

Short bones - carpal and tarsal bones of hands and feet

Irregular bones - vertebrae, some skull bones

Outer shell of a Long bone

compact, dense or cortical bone that encloses a marrow (medullary) cavity that has bone marrow

Tissue located in the ends of the Long bone

Spongy (cancellous bone) that is loosley organized

Diaphysis

shaft of long bone

Epiphysis

expanded portion at each end of long bone

Epiphyseal plate

hyaline cartilage separating marrow cavities of epiphysis and diaphysis; seen in children

Flat bone feature

sandwich arrangement of inner and outer layers of compact bone

Middle layer is spongy bone

Dipole

The spongy bone in the skull

What are the four types of bone cells?

Osteogenic, osteocytes, Osteoblasts, and osteoclasts

What do osteogenic cells do?

They are stem cells that give rise to osteoblasts

What are Osteocytes?

former osteoblasts trapped in the matrix they deposited

What do Osteoblasts do?

Form bones organic matter and promote mineralization

Osteogenesis

Bone-building activity of osteoblasts

Where do Osteocytes reside?

In the lacunae, interconnected by canaliculi

What do Osteocytes detect?

stress on bone and stimulate remodeling

What are Osteoclasts?

Bone-dissolving macrophages; in endosteum and osteogenic layer of periosteum

Osteolysis

the bone breakdown actions of Osteoclasts

How do Osteoclasts dissolve the bone matrix?

By secreting hydrochloric acid (HCl) to bone surface

How do osteoclasts digest organic bone matrix?

Using lysosomal enzymes

What makes blood cells in bones?

Red bone marrow

How do bones help keep electrolyte balance?

By acting as a reservoir for calcium and phosphate.

Main organic component of the bone matrix

Collagen

Main inorganic component of the bone Matrix

Hydroxyapatite and calcium carbonate

How do bones help acid-base balance?

Buffer pH changes by absorbing or releasing alkaline salts

Hormones secreted by bone

Osteocalcin and lipocalcin 2

What are the primary features of compact bone?

The Concentric lamellae, the Osteon, Perforating canals, Circumferential canals, and the Interstitial lamellae

What is compact bone?

The dense outer shell of a long bone

What is the concentric lamellae of compact bone?

layers of matrix around a central (osteonic or haversian) canal; looks like tree rings

what is the Osteon of compact bone?

the basic structural unit; has a central canal and its lamellae

What are perforating canals?

transverse passages that connect central canals of adjacent osteons

what are Circumferential lamellae?

layers of matrix around inner and outer boundaries of compact bone

What is interstitial lamellae?

Irregular patches of lamellae; old osteons that were remodeled

What are spicules and trabeculae and where can they be found?

found in Spongy bone;

spicules are rods or spines (lattice of slivers) of bone;

trabeculae are thin plates and beams

Spongy bone feature examples.

Porous, bone marrow-filled spaces, matrix has lamellae but not in concentric layers, and no osteons

Where are trabeculae arranged in spongy bone?

Along its line of stress